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Rob Wielgus noticed something interesting when he studied reports of wolf attacks on sheep and cattle in the Northern Rockies.

When wolves were killed to reduce livestock predation, the number of dead sheep and cows rose the following year.

“It’s counterintuitive,” Wielgus, director of Washington State University’s Large Carnivore Conservation Lab, said of the study’s results. “People think, let’s kill the wolves and get rid of the problem. But it doesn’t work that way with carnivores. Sometimes, the punitive solution is causing the problem.”

Shooting or trapping problem wolves, particularly the pack’s leaders, disrupts the pack’s social structure. “If you kill the alpha male and female, the pack fractures,” he said. “Instead of one breeding pair, you may have two or three.”

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More pups are born the next spring and the potential for livestock attacks increases, Wielgus said.

His research, published Wednesday in the journal PLOS ONE, questions the accepted practice of killing wolves that prey on livestock. It analyzed 25 years of data from Idaho, Montana and Wyoming.

More dead wolves correlated with more dead livestock, until more than 25 percent of a state’s wolf population was removed, Wielgus (pictured, right) and data analyst Kaylie Peebles found. Then, both the number of wolves and the number of livestock attacks dropped the following year.

Wielgus’s study is partly funded by Washington Department of Fish and Wildlife. The work is the first phase of an $80,000, two-year research project paid for by WSU and the agency. The study’s second phase will focus on preventing wolf attacks on livestock.

The research follows a tense summer between ranchers and wolves in Northeast Washington.

In a highly publicized incident, the breeding female from the Huckleberry Pack was killed by a wildlife agent after the pack killed or injured 33 sheep.

In 2012, the Washington Department of Fish and Wildlife killed seven members of the Wedge pack after the wolves repeatedly attacked cattle owned by a Stevens County rancher.

The northeast corner of the state is home to 12 of Washington’s 15 wolf packs, and also has an active livestock industry.

John Pierce, the department’s chief wildlife scientist, said the research isn’t making the agency re-think its actions.

“If his findings are true – and I think of them more as hypotheses – our typical understanding of how animals react to lethal control is not intuitive for wolves,” he said. “By removing the resident animals, you might exacerbate the situation” in the long-term.

But that doesn’t reduce the short-term value of killing wolves to halt ongoing livestock attacks, Pierce said.

Both of Washington’s lethal control actions were limited in scope, designed to address continued attacks by specific packs, he said.

Agency officials are eager to see the second phase of Wielgus’s research on preventative measures, Pierce said. That work includes mapping Northeastern Washington to determine where wolf-livestock conflicts are likely to occur, based on what researchers know about pack size, livestock location, landscape characteristics and the abundance of deer and elk.

“We’re hoping to get into a proactive mode,” Pierce said. “We’re interested in identifying which non-lethal measures are most effective for preventing future conflicts.”

Wielgus is working on parallel reseach, where both wolves and livestock were collared in Northeast Washington, the Cascades and the Colville Indian Reservation to study the animals’ interactions. For those herds, the use of range riders, noise-makers and flashing lights at night were successful in preventing wolf attacks over the summer, he said.

Meanwhile, Wielgus said the research’s first phase offers important insights for wildlife managers across the West. But whether the study’s conclusions will influence future policy remains to be seen, he said.

“Often, policy is not based on facts,” Wielgus said. “People want predators to be killed, so that will happen, even if it generates more trouble in the future.”